Cataract extraction is a frequently performed surgical procedure. Cataracts are formed when the crystalline lens of the eye opacifies. The cataract scatters light passing through the lens and may perceptibly degrade vision. A cataract can vary in degree from slight to complete opacity. Early in the development of an age-related cataract, the power of the lens may increase, causing near-sightedness (myopia). Gradual yellowing and opacification of the lens may reduce the perception of blue colors as those shorter wavelengths are more strongly absorbed and scattered within the cataractous lens. Over time, cataract formation may progress and gradually result in progressive vision loss.
Cataract treatment often involves eye surgery to remove the opaque crystalline lens. The cataractous lens is then replaced with an artificial intraocular lens (IOL). Each year, an estimated 19 million cataract surgeries are performed worldwide.
During cataract surgery, a technique termed phacoemulsification can be used, wherein an ultrasonic tip with associated irrigation and aspiration ports is used to sculpt the relatively hard nucleus of the lens to facilitate removal through an opening made in the anterior lens capsule. The nucleus of the lens is contained within an outer membrane of the lens that is referred to as the lens capsule. Access to the lens nucleus can be provided by making an incision in the shape of a small round hole in the anterior side of the lens capsule. This procedure is referred to as an anterior capsulorhexis when manual tools are used for making the incisions, and as an anterior capsulotomy when a surgical laser system is used instead.
Previously, manual tools such as microkeratomes were used for making incisions such as those in the lens capsule to provide access to the lens nucleus. Over the years, however, surgical laser systems have become the tool of choice as they tend to lessen the chance of irregular, imprecise and inaccurate cuts and related complications. Laser eye surgery systems have been developed for various cataract procedures, including for instance: (1) creating one or more primary incisions or sideport incisions in the cornea to provide access for a cataract surgery instrument (such as a phacoemulsification tip) and/or to provide access for implantation of an intraocular lens, (2) incising the anterior lens capsule (anterior capsulotomy) to provide access for removing a cataractous lens, (3) segmenting and/or fragmenting a cataractous lens, (4) incising the posterior lens capsule (posterior capsulotomy) for various cataract-related procedures, and/or (5) creating one or more arcuate incisions in the cornea or in the limbus to reshape the cornea for treating refractive conditions.
Accurate placement of a capsulotomy incision, a primary incision, a sideport incision, and an arcuate incision can be important for achieving a successful outcome of cataract surgery. In automated laser surgical procedures, physicians generally provide the necessary parameters for identifying the number, the placement and the size of incisions based on pre-treatment measurements. But, errors in data entry or lack of proper calibration of the laser surgical system can potentially lead to the placement of incisions at locations other than at the locations prescribed by the user. Moreover, some laser surgery systems do not allow real time confirmation of the location of the incision at the predetermined location, or do not provide warnings to the user if the actual placement of incisions during an automated scan is different from the intended location of those incisions.
Thus, methods and systems that introduce additional safeguards, such as verifying the location of a laser scan or ocular incision, would be helpful for treating patients with laser surgical systems.